I Need Some Help Please. Car Pops Out Of Intake.

Discussion in 'Fox 5.0 Mustang Tech' started by erniet17, Sep 9, 2013.


  1. erniet17

    erniet17 Member

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    Yes it was. Dyno'd at 819 on 18lbs but my C4 never stood a chance. It blew twice and never even made it to the track. I was gonna have to keep spending money on it and the underhood temps were bad. I tried different fans, installed an electric water pump and had a cowl hood. Non of that helped. The best fan was the OEM one but it couldn't keep it cool at idle. So... I sold the drivetrain and put the money into my new home.

    I thought I'd have less headaches with a stock H/C/I but boy was I wrong.
    #21
  2. erniet17

    erniet17 Member

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    Ok, I got around to messing with the car today. I cleaned the IAC, tested the power wire to the IAC, bypassed the NSS at the pedal (even though it's new), did the cylinder balance test and checked the voltage at the fuel pump. I also reset the base idle and set my TPS at .98.

    The cylinder balance test came out okay. I got a code "9".

    Now my codes are as follows...

    KOEO: 81,82,85,84
    KOER: 12,91,33

    The car has been running better but still pops out of the intake under acceleration. It will run better when it's really warmed up. I double-clutched it today while it was popping and it responded very good.

    I'm not sure if maybe my -10 feed lines are too much for the amount of fuel that the car requires now. I read somewhere that too big of a line can cause a lean condition under acceleration.
    #22
  3. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

    Revised 06-Sep-2012 remove smog pump crossover tube reference

    Code 41 is a RH side sensor, as viewed from the driver's seat.
    Code 91 is the LH side sensor, as viewed from the driver's seat.

    Code 172 is the RH side sensor, as viewed from the driver's seat.
    Code 176 is the LH side sensor, as viewed from the driver's seat.

    The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

    The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
    "When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

    When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

    Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

    Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

    Testing the O2 sensors 87-93 5.0 Mustangs
    Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear.

    Disconnect the O2 sensor from the harness and use the body side O2 sensor harness as the starting point for testing. Do not measure the resistance of the O2 sensor , you may damage it. Resistance measurements for the O2 sensor harness are made with one meter lead on the O2 sensor harness and the other meter lead on the computer wire or pin for the O2 sensor.

    Backside view of the computer wiring connector:
    [​IMG]

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    The computer pins are 29 (LH O2 with a Gray/Lt blue wire) and 43 (RH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    Testing the O2 sensors 94-95 5.0 Mustangs
    Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


    Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

    Testing the O2 sensor wiring harness
    Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

    87-90 5.0 Mustangs:
    Computer pin 43 Dark blue/Lt green – LH O2 sensor
    Computer pin 29 Dark Green/Pink – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
    From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 43

    91-93 5.0 Mustangs:
    Computer pin 43 Red/Black – LH O2 sensor
    Computer pin 29 Gray/Lt blue – RH O2 sensor
    Disconnect the connector from the O2 sensor and measure the resistance:
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 29

    94-95 5.0 Mustangs:
    Computer pin 29 Red/Black – LH O2 sensor
    Computer pin 27 Gray/Lt blue – RH O2 sensor
    From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
    From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 27

    There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged and the contacts are clean and not coated with oil.

    The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

    Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

    Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

    If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
    Last edited: Sep 21, 2013
    #23
  4. erniet17

    erniet17 Member

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    Thanks, I'll try to perform the test tomorrow. I replaced the sensors with OEM units in late April and they have less than 500 miles. But who knows.
    #24
  5. erniet17

    erniet17 Member

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    Jrichker, we all know that these cars will run without the O2 sensors, which is why it's driving me crazy. I ran this car without the sensors for some time. What else can cause this? What are your thoughts on the -10 feed line?
    #25
  6. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Yes they will run without O2 sensors, but it runs in "Limp Mode" unless you had a custom tune to bypass them in the computer's program. Limp mode means reduced power, drivability and economy.

    The size of the feed line is irrelevant as long as the rated pressure is maintained at the 37-39 PSI

    Back to the beginning: Backfire out of the intake is a lean mixture, sticking valve or spark plug firing at the wrong time. The code 91 tells you that you have a lean mixture on the LH side of the engine as viewed from the driver's seat. Check the O2 sensor wiring as described in my code 41/91 post. If it checks out OK, start looking for things on the driver's side that affect vacuum (vacuum leak), or a sticky valve (detect with a vacuum gauge). Spark plug wires that leak spark or are tied together parallel to each other for long distances can induce a spark or misfire or backfire.

    Finding vacuum leaks

    Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.

    There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.

    Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.

    Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...

    The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.

    The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.

    Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.

    Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
    http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

    Most of the links above have store locators for find a store in your area.

    Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.



    Diagram courtesy of Tmoss & Stang&2birds
    [​IMG]


    Vacuum leak due to slipped lower intake manifold gasket...

    Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.

    [​IMG]



    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

    Ignition switch wiring
    http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

    Fuel, alternator, A/C and ignition wiring
    http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

    Vacuum diagram 89-93 Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

    HVAC vacuum diagram
    http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

    TFI module differences & pinout
    http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

    Fuse box layout
    http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
    Last edited: Sep 21, 2013
    #26
  7. erniet17

    erniet17 Member

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    Thanks. I bought a vacuum gauge yesterday and I'm gonna try to play with the car today. The weather sucks right now.
    #27
  8. erniet17

    erniet17 Member

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    Okay...I think it's fixed. I have about 10mm of vacuum at idle. I double checked the timing. It is set at 18 spout out. About 22 spout in. I decided to reinstall the EGR and get rid of the simulator and that seems to have solved it. Maybe the simulator crapped out. I forgot to plug in the O2 harness and test drove it and it drove perfectly. I pulled the codes when I got back and this is what I have now: KOEO 67,81,82,85,84.......KOER 94,44,33.

    I will update once I get some more time behind the wheel.
    #28
  9. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    10 MM? Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM.. Your timing is way too advanced: 14 degrees is the max recommended for a street driven car and no custom tune. The computer advances the timing according to its internal program. You should not run over 36-38 degrees total advance for both static setting and computer program combined.
    #29
  10. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    yeah, that timing is a bit high
    #30
  11. erniet17

    erniet17 Member

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    The shortblock was in my car when I bought it. I installed the turbo kit on it, used it for about a year, sold it for $50 and came across it on craigslist after 2 years or so. I bought it back for $50 and the guy never installed it. I remember not having much vacuum when it had the turbo setup. I had to run a softer spring on the BOV. Also, I did a leakdown test and most cylinder were at about 15-20%. Maybe the booster?? My brakes are kind of crappy.

    I had it at 16* before. I'm gonna to bring it down some but I have to play with the fuel lines because they exit out of the front and are -8 and they hit the TFI.
    #31

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